I politely disagree. TOS may have been revolutionary for its time, but it hasn't aged well. The writing and acting pale in comparison to TNG, as do the special effects, music, and practically anything else you can think of. I tried watching it, but after a few dozen episodes I had to give up because it was such a bore...
I respect TOS for what it accomplished and generally enjoy it when I watch. I wouldn't call it a bore but it's understandable as sometimes it plods along, and the plywood ship and planetary "foam boulders" sets definitely require me to suspend disbelief a bit much in spots. Overall, I don't revisit it nearly as often as I do TNG.